There could be several reasons to why content seems to be coming in slowly. They could still be having problems with their engine. Something that no one is going to be told or explained. Why would the development team explain their hoop jumping in the development process? To have players jump ship earlier than they want you to?

There could be no problem at all and the game just needed a catalyst to propel their content, make sure everything is cohesive to the already implemented world, and bug free.

Also, I don't know how people can sit there and act like re-development is as easy as one, two, three. Creating a system and it's foundation is miles easier than replacing it into the already implemented world. Since you cannot do this without affecting so many different aspects to the game, you have to make sure everything lines up with this new system. Rather than building this system when starting anew and then working off of that. The balancing in those sort of situations are much easier than what they are doing now.